This invention relates generally to inkjet printing mechanisms, and in particular to techniques for maintaining inkjet printheads at its optimal conditions.
Inkjet printing mechanisms use pens which shoot drops of liquid colorant, referred to generally herein as xe2x80x9cink,xe2x80x9d onto a media sheet. Each pen has a printhead formed with very small nozzles through which the ink drops are fired. To print an image, each printhead is propelled back and forth across the media sheet, shooting drops of ink in a desired pattern as it moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as those using piezoelectric or thermal printhead technology.
To clean and protect the printhead, typically a conventional xe2x80x9cwiper assemblyxe2x80x9d mechanism is mounted within the housing of the printing mechanism so the printheads can be moved to a wiping region over the assembly for maintenance, specifically for wiping off ink residue as well as any paper dust or other debris that has collected on the printheads. Normally, a printhead needs wiping after a certain amount of printing operations or a certain period of idleness.
For a printing mechanism having more than one printhead, conventionally, all the printheads move to the wiping region together. Several flexible wiper-blades in close proximity to each other are provided in the conventional wiper assembly to wipe all the printheads simultaneously.
However, different printheads may have different needs for maintenance due to different characteristics and usage during printing operations. The fact that one printhead needs wiping normally does not justify the wiping of the other printheads. If all the printheads are wiped at the same time whenever one of them needs wiping, the printheads may be exposed to excessive amount of wiping. Potentially, such excessive wiping of the printheads may deteriorate the health of the printheads.
Furthermore, it is also observed that the conventional wiper assembly may cause an unwanted increase in the width of the printing mechanism. Such an unwanted increase in width may be undesirable, especially for printing mechanisms having very limited space.
Take a printer with two printheads for example. As shown in FIG. 3A, the conventional wiper assembly is conventionally positioned at one side, for example the right side, of the printer out of the printing area 106 within which ink drops are projected from at least one of the printheads onto a media sheet for imprinting images. During wiping operations, both printheads have to travel out of the printing area to be above the wiper assembly for wiping. On the other hand, during printing operations, only the right pen 305 needs to travel out of the printing area to allow the left pen 303 to shoot ink drops onto the right edge of the media sheet. Thus, in the design as shown in FIG. 3A, the printheads travel a longer distance to the right during wiping operations than during the printing operations. Such a longer distance may unnecessarily increase the width of the printing mechanism.
Therefore, there is a need for an improved printhead wiping mechanism which optimizes the amount of wiping for different printheads. There is a further need for an improved wiping mechanism that does not cause the unwanted increase in width of the printing mechanism.
According to an aspect of the present invention, in a method for independently wiping a first and a second printhead of an inkjet printing device, a first and a second wiping assembly separated from each other are provided in the printing device. When the first wiping assembly wipes the first printhead, the second wiping assembly is separated from the second printhead so that the second wiping assembly does not simultaneously wipe the second printhead. When the second wiping assembly wipes the second printhead, however, the first wiping assembly is separated from the first printhead so that the first wiping assembly does not simultaneously wipe the first printhead.
According to a second aspect of the present invention, a method for wiping a first and a second printhead of an inkjet printing mechanism is provided. The printheads are movable along a scanning axis in the printing mechanism. In addition, a first and a second wiping assembly are respectively provided at a first and a second wiping region. These regions are separated by a substantial distance from each other along the scanning axis. During wiping operations, both printheads are moved together to, for example, the first wiping region where the first wiping assembly is located, and the first wiping assembly subsequently wipes the first printhead, without the second printhead being simultaneously wiped by the second wiping assembly.
According to a further aspect of the invention, an inkjet printing mechanism includes a chassis, a first and a second printhead, and a carriage supported by the chassis for transporting both printheads along a scanning axis. The printing mechanism includes a first wiping assembly located at a first wiping region for wiping the first printhead when the carriage moves to the first wiping region. The printing mechanism further includes a second wiping assembly located at a second wiping region for wiping the second printhead when the carriage moves to the second wiping region. According to the invention, the first and second wiping regions are separated by a substantial distance from each other along the scanning axis. Therefore, the two printheads are wiped independently by the two wiping assemblies respectively.
The printing mechanism generally has a printing area extending along the scanning axis, within which area ink drops are projected from at least one of the printheads onto a media sheet for imprinting images on it. Preferably, the first and second wiping assemblies are located at the opposite ends out of the printing area. The printing mechanism also has a sweeping area extending along the scanning axis, within which area the printheads travel during printing operations. Ideally, the wiping assemblies are located within the sweeping area for minimizing a width of the printing mechanism.
Other aspects and advantages of the invention will become apparent from the following detailed description in conjunction with the accompanying drawings; the description illustrates by way of example the principles of the invention.